Remote-control and supervisory control system



Dec. 29, 1953 J. A, DCREMUS ET AL REMOTE-CONTROL AND sUPERvIsoRY CONTROL SYSTEM 4 sheets-sheet 1 'Filed April 19, 1951 ZQCEw 952mm Alfy.

Dec. 29, 1953 J. A. DOREMUS ET A1.

REMOTE-CONTROL AND sUPERvIsoRY CONTROL. SYSTEM 4 Sheets-Sheet 2 Filed April 19, 1951 vvvvv QB?. vw. Sam www. mm.

Dec. 29, 1953 J. A. DoREMUs ET AL REMOTE-CONTROL AND SUPERVISORY CONTROL SYSTEM Filed April 19, 1951 4 Sheets-Sheen. 5

IN V EN TORS John A. Doremus By Herber G Waterman Aify Dec. 29, 1953 J. A. DoREMUs ET AL REMOTE-CONTROL AND SUPERVISORY CONTROL SYSTEM 4 Sheets-Sheet 4 ed April 19, 1951 NP a IPH Edil f egnm e 4 wmmmm Sm u zdz :St

Patented Dec. 29, 1953 REMOTE-CONTROL AND SUPERVISORY CONTROL SYSTEM John A. Doremus and Herbert C. Waterman, Chicago, Ill., assignors to Motorola, Inc., Chicago, Ill., a corporation of Illinois Application April 19, 1951, Serial No. 221,916

Claims. (C1. 340-163) This invention relates generally to supervisory control systems, and more particularly to a supervisory control system in which equipment at a remote station is controlled at a central station and indications are automatically provided at the central station showing the actual condition of operation of the equipment at the remote station.

There are many applications in which it is desired to control equipment which must be located at a given point from a central control station which may be remote from the given point. For example, in a power system it may be desirable to control motors, circuit breakers, valves lor any other similar equipment from a central control station. For the operator at the central station to have complete control over the equipment at the remote station it is necessary that the operator know at all times the condition of the remote equipment. That is, he should know that the equipment has responded to the controls initiated at the central station and also whether the equipment has changed condition because of automatic controls or controls actuated at the remote station. Considering for example an automatic circuit breaker, the operator at thecentral station must be advised when the circuit breaker opens automatically due to an overload.

In order to simplify this equipment, it is desired that the control of the remote equipment from the central station be arranged to require a minimum of equipment at the stations and preferably require only a single channel for the interconnections between the two stations. It is also desired that the equipment be so constructed that mistakes in the operation thereof be minimized. By the use of signals of different characteristics, it is possible to transmit a large number of different control signals over a single channel. Similarly, it is desired to transmit signals indicating the condition of the remote equipment to the central station by use of equipment which is simple and inexpensive. Such signals may also have distinguishing characteristics and thereby a. plurality of diierent signals may be transmitted over a single channel. However, a difficulty arises in this instance in that a plurality of operations may take place at the remote station simultaneously and if the control signals are transmitted simultaneously over a single channel the signals might interfere with each other and no clear indication of what had taken place would be received at the central control station.

- It is therefore an object of the present invention to provide an improved supervisory control system for controlling remote equipment from a central station and indicating the condition of the remote equipment at the central station.

Another object of this invention is the provision of a relatively simple system for controlling remote equipment including provisions which prevent transmission of signals having diiferent characteristics over a single channel and which prevents improper operation because of interference between the diiierent signals. y

A further object of this invention is to provide a supervisory control system in which equipment at a remote station is controlled from a central station and indications are provided at the central station showing the condition of the equipment at the remote station and automatically indicating any change in condition whether such change results from a control operated at the central station or from any other cause Whatever.

A still further object of this invention is to provide a system which automatically transmits signals initiated from a plurality of sources in a predetermined sequence so that signals may be initiated by a plurality of sources at the same time or about the same time and are then transmitted in sequence over a single channel.

A feature of this invention is the provision of a supervisory control system by which equipment at a remote station is controlled from a central station by signals having dilferent characteristics which are transmitted in sequence over a single channel, and which includes indicating equipment at the central station operated by signals transmitted from the remote station which also have different characteristics to selectively indicate the condition of the equipment at the remote station.

A further feature of this invention is the provision of a system for transmitting signals indicating the condition of a plurality of items of equipment which may change their operating condition at any time and a number of which may change their operating cond1tion at substantially the same time, with the signals being transmitted automatically and in a predetermined sequence when a change takes place.

A still further feature of this invention is the provision of a remote indicating system for indicating the condition of a plurality of items of equipment and which includes relays associated with each item of equipment which are individually operated when the condition of the associated item changes its operating condition, and `a ment associated with a relay which is operated until indications have been transmitted y fon all equipment which has changed its operating 'onldition. K Y n Further objects and features and thattending advantages of the invention will bie apparent a consideration of the following description whenM taken in connection with the accompanying drawings in which:

Fig. 1 illustrates the control systemV in diagram form;

Fig.- 2 illustrates tiietequi-pnrent provided at' tletr entr'al station;

3` illustrates .the equipment provided at' a remote station; and` A A Fig-r iiiustrotos inodinsd contrai. station equip- Inp f'ct supe f 'y atli c '-al Station can: control veqiii'prrrentjv at a' remote" stationwithl the system1 including means for indicating at the central station th condition' of operation orV the remote equipment. The oon- 'tlals'iati'oii-Ifilay includea control panel forfa'p- Flying dividual c'ontrlsignalsi-havingi different' character" tics to acommunication channel icou; pled to kthe remotestation to selectively control thequ ment at-the remotestation.V Iflie ce'n` lf'tlstatil eliui'i'merit'y isf arranged sf'that the' control signa-is cannot be' transmitted simili--`v iing the" invention thereisprovidd "control system by which arr operator remote station, selector means are providedfor dperatirlglvariouscircuits` in 'responseto the signalsirecivd These circuits may be used to cntrfliarious equipment suchlas' circuit breakvision ofr ace'ntrifugalfswitch onth'e n'iotor'-, la' ciifooit-*molyb's oiosodwhentne motor is operating andLonened-wiiiiof theniotor islet resta y B'y indi'f4 ca'ti'ng4 th corditior'i"r ofP this: circuiti-j aj positive indication is given as to the conditiwnjof the rr'iotiji.;` The equipment; operates*automaticallyto giye the" indication whe'rr any change in `conditiony tintedE dtgtie centrar stationl or' logis any other rririst is'gthe edip'inent attherejnote's't'a; A vcontrol'ai'jb'oththe clenftial andfrinotestations', and` Anii'ay Yalscibe subj ect to automatic control'such as is the case of a cir'- cui-t breakermwhichbmay be throwntopyenv by an ovcrlo'adl, 'Ihe-indi-cation'vmayf besuch to identify theiorigingof the initiating-operation? The transmittingL systeinoperates to send the signals indicating ,thel condition ofgtheiequipment in se`z quenceb soY` that inthe; eventiJ thev operating` con?" ditionoifa pluralityfofl equipmentschangeset the" same time or about the same time, the signals indicating the condition will not be superimposed but will be sent separately.

Referring now to the drawings, in Fig. 1 there is illustrated in block. diagram form the complete supervisory control system positioned at the centra] station andai; the remote station; The central station equipment includes the control panel i0, the tone generator I I, the tone selector I2 and an amplifier and hybrid unit I3. The control panel includes 'al plurality of keys or switches I4 individually associated with items of equipment at the remote stationfor selecting the various items fo `oritrolling the same. In Fig. 1 switches floricoiitrgl'lirigiteiris numbered I to 5 are Shown. Keys' or switches is; is, l1 and is sie provided through which various operations of the remote equipmentare provided by use of tones transmittedv to the remote station. Although a system is described in which signals of diierentsfrequen-oies'` tones die transmitted to" provides@ lective operation; it is obvious thatv signals diffV tering in other respects" can be' used in the same way. Thez switches I5' and'v I6 are for; controlling' the equipment between two conditions indica d' trip and* close,l and the switch I1 is for rele A thov controlled eou'ipinont after the desired 'oon-v trol has beenperfvormed. Switch IS is for caus. ing the' equipment gatt the remote' Station which sendsv back the i'r'ilicat'ion,V to scsi-nv al o f the'. items'. of equipment' and oneoi the condition thereof at any-desired time.- u I. Y

The Connor psneidisjo inoindosrsgpiuisiits or indivertingl lamps identidades I9', 2a andern wnionindicateA the condition' of the' quipmerztt` con?A tro'lled;` The lamps [9?. "tl'an'd- ZIv are associated withr the" individuaiitinsf of eduipinentns aref the sitiitohes`I ldwit'n tno' idnip i9' indio'sitingYv tiviijonA the equipment has been; selectdv'lfor coni-,roland thel -isinns 'zu and' @indicating tnqoondition or operation of i they equipment. The lamps are `cron-4 tr'oiiedty tnstons'sisotoi equipment Antonino-n1 tonesl of*` different"4 frequencies are applied froi'L maremoto-station" ndjwhiononeratosvto jenenv gizei the' la'nfi'p selectively depending' upon thel tonsreceived.' I l Y Attn@ remote-station;- ooin'i'nuniootion is provided witnY the` contrai station triton-gni the ainpiifier and hybrid unit 22. Y'ri'itfs`igna1'-received by' tnouniti 22- front the Ycontraistation isnt-plied to' the tone seltor'- 23'A which produces various oontrorvoitagesfdepending upon the signo-'1s ifo:

ceived.' These control'voltags are'applied o'thef point relaysl 2l"wliicli 'are indiviyqliially' asso r ated With"tlie` various itemsfof equipmentnuniberedj l' to; 5 inclusivefV Col lolvolta'gesifrom thftoi'ieV selector are also applied' to the release circuitj'25`;

th'etripl circuit 2 6 i i the 'close' circuit 2 if and' to the supervisory signal"transinittingv iriea' ri's" 23; TheVN release circuit`2`5`is` oiinected to thevaliouspoint relai/S124 and-td the supervisory signal'tra'sl' mitting moons zeros' releasingtiie'sonif when a particularV signalV isV transmitted tof the rei'ii'ot'e'l station from the" central' station; The' trip and' clo'secircuit'si'and 2 iar'e connected to ith'eva'r# iousitems of equipment''td cause operation thereat` when these equipments are"selected by' the'vpoint relays'lhi."A "lhese equipments are` individuoiiy oonnie'd to tnesnpor'visoi-y sig'noit'rdnsf-A mitting= niea'iis4 Z''f'or causing' operation' thereof to transmit signdis indicating the condition of' those itemswhen there yis a* change' of condition or' when tho'rsnpoivzisory signer transmitting" means is caused to scan all of the equipmnts signals sro"oontin-uousiy`- provided-by th tons generator 30 to the supervisory signal transto` the amplifier and'hybridunit 22- from which they` are applied to the amplifier at the central station.

The tones applied by the transmitting equipment through the amplifier and hybrid 22 to the central station are `received by the'amplier and hybrid `I3 and applied to the tone selector I2 which provides selective controls in response to the particular signals received. Selective controls in the tone selector I2 operate to energize the various indicating lamps on the control panel. In Fig. Zthere is shown the circuit at the central station including the operating keys and the arrangement for providing the desired interlocking relation between the various indicatinglan'ips.

The same reference numerals are used asin Fig. 1 for corresponding parts, and'only the portion of the unit required for the Nos. 1, 2 and 3 equipments are shown to simplify the disclosure.

The switches le associated with the various equipments have pull type operating members which may be pulled out and allowed to remain in the actuated position. These switches include a relatively large number of movable contacts, including contacts |70 and which are effective to make connection to contacts |12 and |13 respectively when a switch is pulled out. The contacts |`l2 and |73, labelled T are connected to the tone generator, and the tones therefrom are applied through contacts Il and I'iI to the conductors l'li and |15, from which they are transmitted as will be further explained. Back contacts are provided which are engaged by the contacts |10 and I'il when the switches are in their normal position so that the circuits are held continuous through the various switches. Each of the switches i also includes a set of contacts for controlling the circuit for transmitting the tones. These include a main movable contact I'I'I normally engaging a contact |18 and engaging the `contact |l9 when the switch is pulled out. The

contact I'l8 engages the contact 80 as the switch is pulled out to provide momentary connection between I'I'l and I 80 for grounding the contact ITI. A further set of contacts is provided on each. switch l@ for controlling the indicating lamps. The contact |85 normally engages a xed contact |85 connected in a circuit to be explained more in detail and `when the switch is operated the movable contact' |85 is connected to the contact |8`| connected to ground.

The switches I5, l and |3 for controlling the trip, close the scan operations, may be substantially identical to the switches I for the various points associated with items of equipment. The switches I5 and I6 for trip and close operation are spring biased and must be held operative for an interval long enough to transmit the desired tones.. Vrl'he switch I8, like the switches I4, is not spring biased and will remain in operated condition until physically moved to the normal position. These switches include contacts for connecting to the tones T from the tone generator and for providing the control operations for transmitting the tones. The release switch il may be :of very simple construction since it includes only asingle contact which is normally open and which is closed when the switchV is actuated. This switch is also spring biased and therefore autoimatically returns to the normal position when released.

and hybrid unit 'The circuit for transmitting the tones includes the resistor |82gacross which avoltage -is devel-V 6 oped to charge the condenser |9|. In the normal condition the resistors I 8|-, I 82-form a voltage divider which applies a Vvoltage tothe point |90,l

When using a plus potential of 125 volts and resistors i 8| and |82 of equal value the potential of point |93 will be about 60 volts. YThis voltage charges condenser I9| which is connected in series with diode |92 and resistor |93. Any voltage across the resistor |93 is applied through resistor |94 to the control grid`|96 of the triode |95.

Now when the release switch or key il is op erated, the point I will be grounded through the contacts of the release switch. This will cause the condenser |9| to be discharged through the diode |91. When the release key I I is released so`vl that the ground is removed, 60 volts will again be applied to terminal |90 Aso that the condenser |9I will charge through resistor |93 providing a voltage pulse on the control grid |30 of triode |95 rendering the triodeV conducting so that the relay |98 will be operated. This causes all the movable contacts 200, 20|, 202, 203 and 204 to move to the left. The movable contact 200 operates to apply th-e tones to the output terminal |99 which is connected to the amplifier and hybrid I3 of Fig. 1. The contact 20| closes a holding circuit for the triode |95, through the diode 205, and through further relay contacts'to -be explained hereinafter. The movable contact 203 cooperates with the contacts 206 and 201 to momentarily ground the condenser |9| and then to connect the condenser to the diode 2|0. Contact 202 charges the time constant circuit 235, 230through resistor 208 as will be further explained. l

The diode 2 I 0 is connected through resistor 2| to ground and through resistor 2|2 to the grid 2|3 of the triode 2M. Since the momentary grounding of the condenser. |9| does not completely charge the same, the voltage is applied through the diode 2 |0 to the grid 2|3 of the triode 2M to render the same conducting. This energizes the relay 2|5 so that the movable contacts 2id, 2|?, 2id, 2|9 and 220 thereof areall moved to the left. The contact 2|| provides a holding y circuit for the triode 2|4 in the event that relay |98 is operated. That is, a holding circuit is provided from plus potential through resistor 209, contact 202, contact 2| 0 and resistor 2|'2 tothe grid 2 I3 of tube 2M. The contact 2|1'charges the time constant circuit 231, 238 for the triode |95 through the same resistor209l Contact 20 I ,diode 205 and resistor .les connect the grid |96 to the time constant circuit 231, 238. Contacts 2|8 and Ele when in the left position are connected to tones from the tone generator which are used to indicate release. After the time constant circuit 231, 238 discharges, triode`|95 no longer conducts, releasing Vrelay |98. This allows time constant circuit 235, 235 todischarge, and after its discharge triode 2id no longer conducts, releasing relay 2|5. During the discharge time of 295,

236, that is while relay 2|5 is picked up but relay' |98 has dropped out, no tone signal can be sent out. This provides a guardtirne between successive tone signals which is necessary to prevent improper operation of tone selector equipment 23.

In the unoperated position of the relay 2|5,

contacts 2|8 and 2|9 are connected to the conductors |14 and V35 which apply the'tones from the various selector switches.` The tones from the contacts 2 I0 and 2|9v are applied through rer |98 and` contact .22,0 of relay 2l5are connected inv:

i signal rceived'frcm the remote station' indicates that the circuit breaker 40 is closed this tone will operate through the tone selector to provide a voltage on the grid 26| of the triode section 262. The triode will then conduct and the current will ilow through the winding 263 t connect the lamp 28 to source A to illuminate the same indicating that the circuit breaker is closed. The lamp 2| will be extinguished since the contacts associated with winding 251 are opened 'through the mechanical interlocking arrangement. lThe lamp I9 however will remain energized because of the holding circuit of relay 258 which would be energized by action of the triodev section 262 in any event since current from this section also flows through the relay winding 258 to operate the same.

When the release tones are applied by the remote transmitting equipment, the tone selector I2 will apply a voltage to the grid 265 of triode section 266 causing this triode to conduct to energize the relay 261. This relay includes conltacts 268 which are normally closed to apply plus potential to the contact 259 for the holding cir- @cuit of relay 258. When the relay operates, the contacts 268 open to break the holding circuit `or the winding 258. The operation produced by the release signal therefore extinguishes the lamp 'I9 but allows either the lamp 28 or 2|, which- 'ever is operating, to remain in that condition. `The interlocking arrangement of the lamp 2| and T22 causes one of these lamps to 'be energized at all `times.

In order to provide an indication as to whether a change in the condition of the remote equipment results from a control operation at the central station, or from automatic operations which may take place at the remote stations, an arrangement is provided for causing the lights to ilash on and oi when the change results from a remote operation whereas the lights will be on steady in the event that the operation was initiated at the central station.` This arrangement operates through the ground connections to the lamps I5, 26 and 2|. Considering the circuit associated with the No. 1 equipment, the contact 281 of the switch I4 provides a steady ground to the contact |85 when the switch I4 is actuated. When the switch is not actuated the contact |86 "makes connections to the contact 218 of the relay 25B.. When the relay 258' is not actuated, the contact 21o is grounded to apply steady ground to the lamps I9, 2U and 2|. However, 'when the vrelay 258 is actuated, contact 218 is connected to 'contact 21| which is in turn connected to contact T248 of the scan switch i8. When the scan switch lhas been operated contact 246 engages the contact 24| which is grounded so that a steady ground is applied to the lamps through this contact. However, when the scan switch is not operated the contact 248 engages the contact 242 which is connected to the contact 269 of relay 261, to the contact 234 of relay 238, to the contact 243 of relay 244, and to the contact 245 of relay 246. The contact 269 of relay 261 provides steady ground to the indicating lamps I9, 20 and '2| when the release tones are received and the relay 261 is operated and the contact 234 provides steady ground when either of the tubes |95 or 2 I 4 is operated while tones are being transmitted.

The relay 242 iis connected to the cathode of tube 241 and through resistor 25| to plus B. The

grid of the tube 241 is connected to a positive potential through resistors 249 and 258, but the tube fis 1norinallynon-.conducting .ducto the poshv any one of the relays 258 is actuated. Therefore, the tube 241 will conduct when one of the relays 258 is operated. Therefore, when a steady ground is not applied to the lamps by one of the previously mentioned connections, the tube 241 will conduct when one of the relays 258 is operated. When the tube 241 conducts, the relay 244 will operate and the contact 252 thereof will Vbreak the grid circuit to the triode 241 so that the tube will be blocked and the relay will drop out. The circuit to the grid will then be completed again so that the relay 2534 will intermittently operate and ground will be intermittently applied through the contacts 243 to the lamps.

In order to provide an alarm which may indicate to the operator that something had happened which has been initiated at the remote station, an alarm circuit is provided including the triode 215 in the output circuit of which is the relay 246. When a steady ground is not applied to the lamps by one of the previously mentioned connections, an intermittent potential is applied through the lamps I9, 28 and 2| whenever contact 243 is opened and is rectified by the rectiier 216 to supply a. positive voltage across R-C lter 211, 288, the time constant of which is long enough to maintain tube 215 conducting during the periods of closing of contacts 243. This voltage is applied through resistor 218 to the grid of the triode 215 to cause this triode to conduct and the relay 246 to operate. Therefore the contacts 245 will remain closed to energize the lamps 219. It is obvious that other alarm devices than the lamps 219 may be used if desired.

Therefore, when any one of the switches I4 is operated to provide a control operation, a steady ground connection will be provided to the lights, and after the points are released a steady ground will also be provided. This steady ground will be held continuous through the relay 230 as long as any signal is being transmitted. Further, a steady ground is provided by the scan switch when the scanning operation takes place. However, when operations take place at the remote station causing tones to be transmitted to the central station which will operate one of the relays 258, and in the event that none of the switches are operated at the central controls, an intermittent ground will be provided through the relay 244. Thus flashing of the lights as Well as operation of the alarm circuit will take place.

In Fig. 3 there is illustrated the equipment required at the remote station for controlling the equipment thereat and also for transmitting signals back to the central station to indicate the condition of the remote equipment. The control signals from the central station are applied to the tone selector 23 which selectively provides closed circuits in response to tones of particular frequencies. The tone selector serves to provide energizing voltages at the remote station which correspond to the circuits closed by the switches I4 to I8 of Fig. l at the central station. That is, when equipment No. l, 2 or 5 is selected, the tone vselector operates to apply a voltage to one of the Operation of the trip and close switches at the central station causes ener- -gization of the relays 34 and 35 respectively.

Operation of the release switch at the central station causes operation of the release relay 36 at the remote station and correspondingly operation .of the scan-switch I8 at the central station causes fperation of the scan relay 31 at the remote station. Itis therefore apparent that the tone selector serves to provide operations at the remote station which correspond to the switches in the control panel at the central station.

In the remote station system of Fig. 3, the equipment No. 1 is illustrated as a circuit breaker identified generally as dil. The equipment No. 2 is the motor 4i and the equipment No. 5 is the valve 42. It is to be pointed out that these items are merely illustrative and various other equipment can be controlled in an entirely analogous manner. It Ais also to be noted that a much larger number of different items of equipment can be controlled.

Considering first the circuit breaker 40, this equipment includes windings 43 and 44 for causing the breaker to trip and close respectively. These windings may be selectively connected to ground through the contacts 45 andV 46 respectively of the relay 3i. The relay 3| also includes contacts 41 which establish a holding circuit for the relay and momentarily closing contacts i3 which serve to operate the relay 50 momentarily whenever the relay 3| either opens or closes. As will be more fully explained, the relay 50 will operate to cause a signal to be transmitted to the central station indicating the condition of the equipment No. l. When the No. 1 equipment, the circuit breaker in this case, has been so selected at the central station, the operator may then change the operating condition of the circuit breaker. That is, if the circuit breaker 4U is tripped, the operator may operate switch I6 at the control panel to thereby cause operation of the relay 35 at the remote station to close the circuit breaker. It is apparent from Fig. 3 that operation of the relay 35 causes the contact 5I thereof to be connected to plus B and this energizes the winding 44 of the breaker so that the arm thereof moves to the closed position which is shown in dotted line.

Change in condition of the circuit breaker operates through the contacts 52 and 53 to discon- ,nect the condenser 54 from ground, through which it was connected by contact 52, to plus B through contact 53. With the circuit as shown the condenser 54 is connected across plus B and ground and will therefore be charged to the plus B voltage. This connection is provided through the contact 52 to ground, and through the winding of the relay 58 and the contact 56 of the relay 31 to plus B. Now when the contact 52 is opened and the contact 53 is closed, the condenser 54 is connected to plus B at both terminals so the condenser will discharge. This discharge current flows through the winding of the relay D and causes the relay to operate. If the contact 52 is thereafter made, the condenser 5,4 will again be charged by plus B and the charging current will cause the relay 5B to operate. As will be explained more fully when the relay 5U operates it causes the transmitting system to transmit tones indieating the condition of the equipment associated with the relay. The condition of the circuit breaker is therefore continually indicated at the central station, with the indication closely following all changes in condition so that the operator can check to see that the desired control has actually been performed. l

When no further control of the circuit breaker 40 is required, the release switch will be closed at the central station causing the release relay 36 to operate. This causes the contact 58 thereof to be disengaged plus B .to release .the holding circuits for the relay 3|. and l@i150 Causes the 00ntact 59 to be disengaged from ground to open the circuits through the momentary contacts 48 of the relay 3i so that these contacts will not actuate the relay 5D when the relay 3l is released. The relay 36 also includes contacts 51 which initiate operation of the transmitting equipment to send out release tones as will be more fully described.

The No. 2 equipment is represented as the motor 4| which is'operated by a voltage source AEil through switch 6|. The switch 6i is controlled by the windings 62 and 63 which are connected to the contact 64 and B5 of the relay 32. Therefore when the No. 2 equipment is selected and the relay 32 operated, the contact 6d and 65 will close to connect one terminal of the windings 62 and 63 to ground. The relay 32 also includes contacts 66 for establishing a holding circuit for the relay and momentarily closing contact 61 for energizing the winding of the relay 1 0 which controls the transmitting equipment. The operator can therefore by closing the switch 2 at the control station cause the relay 32 to operate to ground one side of the windings 62 and 63 to thereby select the motor 4l. The equipment at the remote station will then operate to send out a tone to the central station showing the condition of the motor 4I at the time it is selected. The motor is shown with the energizing circuit thereof closed so that the motor will be running. This condition will be indicated to the operator through the control panel.

When the operator decides to stop the motor 4I he will operate the trip switch lr6 which will energize the trip relay 34 and connect the winding $2 to plus B. This will cause the switch 6i to open to stop the motor 4l. For indicating the' condition of the motor, there may be provided a centrifugal switch having a movable contact 1l which may be connected through contact 12 to ground or through contact 13 to plus B. Thek movable contact 1| is connected through condenser 14 to the winding of the relay 10, so that change in position of the movable contact Il causes one terminal of the condenser 14 to be shifted from ground to plus B, or vice versa. This will cause the condenser 14 to be either charged or discharged, and the current therethrough will flow through the winding 1e of the relay to operate the same. Therefore, after the operator has changed the condition of the motor il the relay 10 will again operate to transmit signals which indicate on the control panel at the central station the condition of the motor. If the operator desires to provide no further control of the motor he will then operate the release key I8 causing operation of the release solenoid 36 which will operate to break contacts 5B and 59 to release the holding circuit of the relay 32 and prevent operation of the point relay 1li as the relay 32 closes as previously set forth. The contacts 51 will close to cause the release tones to be transmitted from the remote station to the central station.

The equipment No. 5 at the remote station is indicated as a valve 42. The valve is controlled `by a. solenoid 16 energized by voltage source 11 through switch 18. The switch 18 is controlled by the windings 19 and 88 which have one terminal thereof connected to the contacts Sil and 82 of the relay 33. The relay 33 also includes contacts 83 which provide a holding circuit therefor and momentarily closing contacts 84 for asom;

energizingv the relay kil 5`r whichoperates the transmitting system for sending tones -to -the central station when the No. equipmentor valve. ,-42

`is selected. After-the operator hasnclosed the switch selecting Athe No. 5 equipment he may change the condition ot this equipment by operation of. either the trip or close switch. As shown in Fig. 3, the valveAZ-is shut, and to open the Valve the operator may actuate the trip key which energizes the solenoid 34 and connects'the winding v'|E| to plus. B. through the contact 59.

Opening of thevalve 42 willcause actuation of the switch connected thereto so, that themoving contact 86 will move away fromfthe contact 8l and will engage the contact 8S. The contact ..81 isconnected to ground and the contact 83 is .connected to plus B. The movable contactiis connected to one terminal of the condenser 39 .so that this terminal is shifted from ground to plus .B or viceversa when the moving contact changes from one position .tothe other. VAs in the previous circuits, this will cause the condenser 89 to either charge or discharge and-the current therefrom will flow through therwinding of the relay 235120` actuate thesame. `The relay y85 will therefore initiate operation oi the `transmitting equipment so that signals will betransmitting indicating the condition of the Valve 42 so that the operator at the remote station can determine whether the desired operation has been performed. After operations on the valve 42 have been performed, `the operator can actuate the release key I8 to cause the relay` 35 t'o be energized .and thereby release the holding circuit for the relay The relayt also causes thecontact 59 and 5l to be operated to perform the functions previously stated. 1' Y,

. As previously stated, the ContactV 5l of therelease relay 3s at the remote station operates to transmit tone signals tothe central `station indicating that the equipment operated has been released.: rihe contact lclosesa circuit through relaySIl and the contact 5t of relay 3l forenergizing the relay SIL The circuit is completed through the parallel circuit including condenser 9| and its discharging resistor. QZ whichkare `effective to cause the relay sil topickpupmomentarily and lock in through its own contacts 90e through resistor 9S to ground.` f

*Considering now `the transmitting system,

which is automatically operated in` responsel to operation of any one of the relays 5i), 'likte-and 90. this system includes a spring-driven stepping switch ma having Contact levels mi, un, mais@ and |625.` The stepping switch-includes a spring,

an energizing winding litt whichcocks. the springnand interrupter contactsl |01 to open the cooking circuit when the springmis compressed. The spring itself drives the switch to the next position upon opening of contacts i el. This steppingswitoh vmay be of standard o ccnstruction. as is used in telephone applications and other selecting systems.v Thenumber of contacts,Y required in each level will depend upon the number of items of equipment controlled and the general complexity o the system. `It is possible to use any standardswitch having at least as many contactsper level as vthe nunibeljof equipments controlled plus .additional contacts for. release and for a home position of the switch. As will be eplained, switches-having alargar number V of contacts than necessary can be use d and connections can be provided so that the unused` contacts Willbe rapidly passed over in the operation of the system.

- `'Ihe operat-ion-oi'rgthe lstepping switch -is controlled principallyl through the switchglevel |i l iits own contacts |01, and holding circuits thru resistor- ||l8-which hold it vinV the cocked position. Resistor I2| and condenser |22 provide spari; suppressionfor contacts mi. The home contact of the level I0 I,- marked H is connected to the contacts 50A,-|'0A, 85A and SDA of the relays 50, 10,185 and 90 respectively. These contacts are normally open and are closed when the respective relays are closed to apply plus B potential to the homey contact of the level Ii. The number 2, Sand contacts of the level are connected to the relay contacts 50B, 10B, 3dB and 90B of therelays 50,10, 85 and 96 respectivelyand normally' connect these vcontacts of level lill `to plus-B. `The relays 50, lil, and 95 are called point relays as they provide the connection from thestepping switch tothe various equipments or points.- Whenany-of the relays are operated,-this connection to plus B is broken and the contacts are connectedA to ground through resistors95, 96, 91 and Slrespectively. rhe relays 50, 1.0, 85 and-9|ialso have contacts 50C, "HJC, 35C and C. which are in holding circuits for holding the relays operated. Relays 5D, l', d5 and SC3 :are ofthe-type having a shading coil and coin- `monly described as the A. C. type. Thus, even though theoriginal current which picks up the relaymay `be in either direction (the current may be caused either by charge or discharge of a condenser through the relay winding) and the holdling current is always ingthe same direction, the relay-Will not be lprematurely dropped out because ofpossible current reversal between the pick-up and hold-in conditions.

Thehome contact on level Il is connected to the plate |0 of a triode tube section v| I i. l r)The grid. ||-2` ofthe-triode is also connected to the home terminal through resistor IIS. The movablecontact at level-I 0| is connected to an intermediate tap on the resistor I |3 through condenser ||4 andis connected through the winding of relay kI I5 to the-cathode- IVIG Vof the triode. Relay I |5has acopper slug on its coil to cause drop out delay. `Resistor ||l interconnects the plate IIS andV the cathode- ISof the triode and may be shorted out by the contacts IIS of the relay It. .The relay I|5also includes contacts H and i for apurpose to be described later;

Asecondtriode tube section |25 is provided which may be included in the same envelope with thetriode section I I |.4 The triode section |25 includes a plate IZB connected to plus B, a cathode |-2l` connected through rela-y winding |28 to ground and a grid |29 which is connected through resistor` I3!) and the parallel circuit including variable resistorll and condenser |32 to ground. The grid |29 is also-connected to ground through resistor |39, resistor |3650I and contacts' It? to the contact |20 of `relayfI |5,'and when the relay IIE operates, aconnection-is provided from plus B through the contact |35 of relay |28,resistors ist and'v |36af andl resistor |30 to the grid |29. This renders thetriodesectioni conducting so that the relayl |26 operates and removes the plus B connection. from the .grid |29 of the triode |255. Through this connection the condenser |32 has been charged from plus-B sogthat the triode |25 remains conducting. The relayv |26 also includes contact4 I Bland |38, the function of which will be described-later. if i y .-@Thecontacts |38 of relay |28 operate to connectftones suppliedV from the tone` generator 3e to the conductor I4| which applies the tones to the central .station- .iconneetionzef theltone fgenerator with this ,concluctolaremade through The-connections are such vthat .when the Vswitch Vis in thetposition corresponding tothe individual items lof equipment, tones are connected to lidentify the equipment. That is, when thestepping switch is at contact I, tones are transmitted which identifythecircuit breaker' it. Similarly, when the stepping switchis at contact 2, tones are ,connected which represent the motord and contact 3 connects tones representing thevalve t2.

| I5 serves to ground the tone line, thus preventing tone output, .whenever relay ||5 is picked up.

Considering now the `operation of -the system,

it will be assumed first that the relay 5|! has been actuated. As previously described the relay 5l! may be operated by operation'of the No. switch I at the control panel by the operator through relay 3I and contacts 48 thereof, or through condenser 54 when there isa change. The contact 5ta of relay 5E! operates to provide plus B connection to the home contact of level I which is in turn applied through the interrupting contact lill to the winding |06 of the stepping switch. This causes the stepping switch electromagnet |06 to mechanically cock the switch andy at the completionofthe ,cocking action, open its own circuit I U1. This de-energizes electr-@magnet |56 and allows the cocked Vspring to move the switch one stepso that the movable contacts at all levels of the switch are 'positioned at contact number l. ContactnumberI of level I!!! is connected to contact 5912 of relay ,58, which is connected to resistor 95 in the holding circuit for the relay t, when the relay' is actuated. There is a small voltage drop across the resistor Q5 due to the circuit through the contact lit of the relay 3l and the relay winding 50, but this voltage'is not suflicient toenergize the winding IUS of the stepping switch. The plate llll'of the triod-e III is also connected to B plus through the relay contacts Sila, and the cathode IIS is connected to a lower voltage `since the movable contact at level |||I is connected only to the voltage applied across resistor 9,5. The triode is thus rendered conducting and the relay I5 in the cathode circuit thereof becomesractuated. As-the contacts I8 of the relay I I5 directly short the plate IIG to the cathode v| I6, the relaycoil I |5 is subjected to a higher current than would be possible if the triode I II was allowed to-remain in series. This -is to insuresufcient uxrfor vthevslow release -action, which will -be described later. The relay ||5 operates to close contacts ||9 for a purpose to be described later.

The relay ||5 yoperates -through contacts |20 thereof to remove ground from contacts |31 thereby to provide a voltage ,to the grid |29 of the triode through the connection from plus B through contact of relay |23 and through'resisters |36, |39, and |30, to render this tube v|25 conducting This causes therelay |28 t0 operate and this relay acts through the contacts |35 thereof to immediately remove the'plus'B potential from the grid circuit. 'However' the condenser 32 inthe-grid circuit .has become charged and holds the tube conducting yfor a `predeter- 'no equipment associated :mined inter-val depending upon the ,setting of theresistor :|3| which tends Ato discharge-the condenser |32. When the relay |23 is kOperated plus B is applied through contact |35, contact IIS and contacts |01 to electromagnet |136 of the stepping switch to cock the switch and after contacts Iill `open, to hold it in the cocked position with current through resistor |138. Also, contacts |35 supply B-lthrough contacts H9 to the end of coil H5 which is not connected to contacts ||8. This puts B+ on both ends of coil ||5, allowing it to release, but only after its own drop-out delay. During the slow release time of relay ||5 B-iis connected through contact I9 to the moving .Contact of level ||3| and through the number I contact to the contact of 5th of the relay .5o. As the contact Elib is connected through contact 5Go to the winding of relay 5B, when the relay is actuated, plus B is in effect applied to both terminals of the winding of the relay 5|] and the windingis in eilect shorted so that the relay 5B drops ,out and the holding circuit through contact 530 is broken.

While the relay |28 is operated, the contacts |38 close and after relay II5-drops out, the contacts l2@ open, so that the tones applied to the terminals I of level m2, and either level l|03 or Hifi, will be applied to conductor iilI through resistors |153 and |44. Whether or not the level m3 or |64 is connected depends upon the condition of relay |45. The relay is selectively connected through the level H35 to the switches on the equipment indicating the condition of the equipment. Contact of level il is connected to the switch on the circuit breaker and is connected either to plus B through the contact 53 or to ground through the contact 52. When the switch is in the tripped position as shown, the relay 45 is not operated as the winding thereof is grounded so that the contact its is connected to the level |03. However, when the circuit breaker is closed plus B will be applied from the contact 53 to the winding of the relay |55 to cause this relay to operate and the contact |46 thereof to make connection to the level Illal. Therefore in the position shown-the tone applied to the rst contact of level |02y which is acommon tone identifying the circuit breaker its, and the tone applied to the contact ci level 3, which indicated that the circuit breaker is tripped, will be applied through relay contacts |38 to the conductor lill. Y

As previously stated, after the time relays I|5 and |28 are simultaneously operated, the relay 5U which started the operation will be released, connecting plus B through contact ib to contact of level lill and then to one of the contacts |01. Contacts |01 are held open, however, by current from plus B, contact |35, through resistor |98 to electromagnet H35 until relay i2@ drops to its normal position. When contact iidopens, the stepping switch will then bevdriven by thelspring to the next contact which is contact 2. Contact 2 is connected to plus B through contact 75h of relay l@ so the switch will continue on `through contact 3. Contact 3 is connected to plus B through contact 35h of relay S5 so that the stepping switch will again operate. Contact'll of vlevel ml is connected directly to plus B since there is with this position. Therefore the stepping switch will continue to contact 5 which is the release Contact. lf the release key at the central station has not been operated to cause the relay ll to be operated, the contact Sb of the relay will apply plus 'B 17 to contact of the level IUI so that the stepping switch will continue. Ihe next contact on the stepping switch will be the home contact at which the switch will come to rest in the event none of the point relays are operated.

The various tones applied from the tone generator 36 to the contact of levels |02, |03 and |84 of the stepping switch must be selected so that each diierent condition of the various equipments provides a diierent tone combination. In the system shown, ve different tones are used to provide diierent combinations -for eachcondition which might occur. The number of tones required will of course depend upon the numher of equipment controlled and the various controls required. l fe 'Ihe relay |45 includes a set of momentarily closing contacts |150 which are connected through the contacts |31 of relay |28 to the condenser |32. The purpose of this circuit is to prevent improper operation of the system in the event that an item of equipment changes condition while the transmitting system is in the process -of sending out tones indicating its condition that is, while relay |28 is picked up but after relay II5 has A dropped out. Duringlthisy time the point relay will again be picked-,up whenever-the piece of equipment changes its positionl indicating switch. As previously stated, the tube-|25will remain conducting as long 4as the -condense r,. 32 ,is charged to a predeterminedvalue.-The momentarly closing contacts |50l provideaonnection from .groundrthrough .contacts to thefcondenser |32 through contacts|31 and current 'limiting resistor |3Ea-to dischargegthe condenserf|32 so that the triode willstop conductionjand drop out relay |28. @To Iurther insure'- relay I 28 dropping out, its, groundyreturn isy momentarily openedat contacts 41 Awhen;relayI ftSoperates. Therefore if one-of the `equipment,changescondition while tones are being `sent out to indicate its condition, these tones will bev` immediately stopped, the stepping switch will be moved ontowards home position, .and the'tonesndicating its new condition will be sent as the step switch -comes around again in response to the point relay having been picked up. Thus the proper tones will be sent to cause the proper indication at the central station. e

It will be apparent from the above that when any of switches I 4 or the switch I1 is operated at the central station, one of the point relays 50, 10, 85 or 90 at the remote stationrwill be operated. If the equipment changes .condition due to operation of the trip or close switches, or automatically, a point relay will be set up; In such case the position of the level I UI will be connected to plus B to start operationof the selector switch. The switch will continue until the contact on level IDI associated with the relay operated is reached at which point it will be held for a suflcient length of time so that the tones associated with the equipment may be transmitted to indicate the condition of the equipment. The switch will then continue to the home position at which it will stop. If two of the point relays are operated simultaneously, or near the same time because of changes in the condition of operation of two equipments has taken place, signals indicating the condition of these two equipments may be transmitted on the same sweep of the selector switch. In such case the signals will be transmitted in a predetermined order depending upon the connection of the equipment tothe contacts of the switch, and not description depending upon the order in which the changes took place. That is, even if the equipment connected to contact 3 changes its operation before the equipment connected to contact'Z, the signal indicating the condition of the equipment connected to contact 2 will be transmitted first.

It may be desired by the operator at the control station to check the indications shown on the control panel. To do this he may operate the scan switch I9 which will cause all the point relays to be set up and the selector switch will stop at each position to indicate the condition of the equipment associated therewith. Operation ofthe scan switch at the control station will cause operation of the scan relay 31 at the remote station. This will cause the relay contacts 56 and 38 to momentarily change their position. Operation of contact 5S changes the condition of charge of condensers54, 14, 89 and 9|, charging those which may be connected to ground or minus B at their i respective condition -indicating switches, and discharging-those which may be connectedto plub B `at their respective condition-indicating switches. This will cause all point relays 50, 10, 85, and 90 to pick up. However, since contact 38 opens the circuit through the winding-IMIS Adiz' the stepping switch, the switch cannot start operation until the scan relay 31 has beenfjreleasedg" Releasing the scan relay will lagainnause'charging' or discharging currents to ow'throughrelaycoils 50, 10, 85, and 90 although this action will be redundant in that they are alreadyfpi'cked up. However, reclosing contact 38will allow the stepping switch to start operation and it,will1stop at eachv of the contact points and transmit signals indicating the condiltion ofeach piece of equipment. 'Ihe system will also send the release tones to remove the indicationV at the control station that equipment has .been selected.' Y

l'n Fig. 4 there is illustrated modied central station equipment which may be used in the system of Fig. 1 instead of the equipment illustrated in Fig. 2. AThe same reference numerals are used to designate corresponding parts in Figs. l, 2 and 4. The operating switches and the lamp circuits for only the Nos. I, 2 and 5 equipments are shown as in Fig. 2. The switches are all spring biased push-button type so that they will return to their normal position and need only to beheld in instantaneously-for the associated relay to operate as the holding circuit holds the relays operated until the tones are transmitted.

Each of the switches I4, as well as the switches I5 to I8 inclusive, has associated therewith a relay indicated 30D-3DS respectively. One set of double-throw contacts of each switch and two pairs of contacts on each relay are for connecting the relays in an interloeked manner. relay includes a pair of contacts for transmitting tones from the tone generator tothe amplifier and hybrid I3 for controlling the remote operations. When a switch I4 is operated (moved to the left) contacts y3||l thereof cause operation of the associated relay. .The relay is first energized through the series circuit including the contacts 3|| of therelays, contacts'3l2 of the switches to the right of the switch operated, and contact 3 0 on the switch operated. The other side of the relays may be connected to ground through the conductor 3|3 which is connected through timer 3|5 to be described. Asthe relay is operated the contact 3I6 thereof engages fixed contact 3I1 to hold the relay operative. -The contacts 3| I, which are arranged to open after contact 3|6 Each acca-'554 I9 engages xed contact 3H; tothereby open the series circuit so Athatzanother relay cannot be operated asd long 'as the'rst relay reina-ins operated.' Also, if a. push-button is held` depressed, ther'operation of a-second push-button will not operate another relay, since contacts 3I2orrthe second switch will open to prevent '+B from being applied-through contacts 3FG, 3I'I, of the relay in operation and contact 3I0 of the switch being heldin.

When any one of. the relays operates, the'contacts 3I8 and" 3I9thereof' provide connections fromV the tone generator I'I to the conductor 32D connected to the amplifierv and hybrid unit I3. 'I'hese connections are made through resistors 32! and 322v which provide isolation. After the tones have been transmitted for a predetermined time,

the timer 3I5 operatesr to break the ground connection so that the energized relay drops out and the transmission of the tones therefore ceases. The contact 3I8 of the relay will then close again to restore B plus to the relay contacts connected with the various operating switch contacts.

Considering now the timer 3I5, this timer includes a tube 325 having a relay 323 connected n the cathode lead thereto. The. relay 32S includes movable contacts 32T and 328, with the contact 323 providing a circuit for charging the condenser 329 when the relay is not operated. This circuit is completed through' the normally fclosed contacts 330 of eachof the switches I4 to Iinolusive which'are'connected in series. When ajswitch is operated, the contacts 33! thereof. (all o fj which vare connected in parallel). are vclosed to vconnectjthecondenser 323jdirectlyto the grid 'of the tube 325 throughresist'or' 332; This causes the tnbe1325to vconduct anditherelay321i` to operl'w pperation ofttherelayllf causesthe contact321`to' close to"provde ground'for the various relaysll izo/,336 inclusive.. As the switchia'will bajo perated only momentarily, .thevoltage to` the vrgridjoijthejtube,325 'through the contact 331 will be j maintained only momentarily. However, ,whenithe relay 326 operates, .contact 328 engages a back-'contact 333 which provides an alternative p'atlifor application.v ofthe voltage from con- 'denser'-329Y to the gridof the' tube 325. In this connection variable resistor.334 is connected in parallelto'ccndenser 329 and serves to discharge this; condenser. Therefore the tube 325 will conduct for a predeterminedY time depending upon the `relative values of the condenser 329 and the resistorl 334, to hold the ground connection through contact 321 for this specied time only. Should a push-button be held in after the timer relay 325 drops and releases the one of the varibus relays 380 to 306 inclusive, no relay can again `bey picked up until the pushbutton is released to restore B-I- connection to the timer through series switch contacts 330 to thereby recharge timerI capacitor 329.

It is therefore seen that when any one of the switches I4 to I8 inclusive is operated momentarily, the system will operate to transmit the tones associated therewith for a predetermined time. Also, after any one switch is operated, for the period while the timer holds the relay operative, another relay cannot be rendered operative. There is however no provision for preventing too rapid successive operation of switches in systems that require a guard time between successive tone signals to prevent improper operation of tone selector equipment 23. In such a system it is necessary to use the arrangement shown in Fig. 2 in which the operation of a second switch before the-rst set of tones have been completely' transmitted and a predetermined guard time has vpassed, will cause the transmission of the release dtone so that none of the tones transmitted will be effective to cause an operation Vat the remote station.

In Fig. 4 there is also shown a system for' operation of the indicator lights at the central station, with the lights being designated IS, 20, and 2|- asin the previous embodiments. In this systemthe' lights 2il-and 2I are operated through a latching relay arrangement as in Fig. 2- so that one or the other ofthe lamps will always be energized. The voltages from the tone selector I2 are applied to the grids of the tubes with avoltage -being applied to the grid 343 of the triode 34S when tones are received by the tone selector indicating that the No. l equipment is in tripped condition. This causes the relay 342 to operate so that the armature is moved to theposition shown for connecting the lamp 2|' to thealternating current source A. The cathode? ofthe triodesection 34! is connected to relay 343' to cause this relay to operate when the triode 34| conducts to close contact 344 which energizes the lamp I9. When a tone is received indicatingthat the equipment No. l is inclosed'position, a voltage will be applied to thev grid 3Ii5f1jom'ltheftone selector, which will cause the triodesection 346 to be vconducting and the relay 34Tto.opeifat to move the armature to the alternate positonf'f In such case the lamp 20 wilf be energizedlandf-also lamp I9, as the relay 343 is alsoi -in-l the cathode circuit of the triode 345'." `f' f' -=i1 ff As previously stated;Y the armature Fassociated with the relays 342 :and'34l is always held n'one position so that one'v of the: lamps '2I!"'orlf2 I isv always energized. It fisfds'ired' that th'ref -lamp I @be -energized until the releaseeratiortalies place.- Therefore-'a holding circuiti is'ip'rvided for the relay343 Vthrough itsnntactrliiand through the contact 349 of-relaY-35Iconnectdin thecathodey circuit of `triodi35i The contact 349 is normally closed to hold' tliecircuitthrough the relay-'343,' and'when the' release' tones'l are received a voltage is appliedi'from"ther-tone'y -selector to thegrid of the triode 35 Iso thatv this'tube is'rendered conducting and the relay-'350 operates to open the contact 349 and-thereby release-n re'- lay 343. A single release triode-35I and relay-359 provide holding circuits for all the relays 343.l In the system just described thereA no arrangement for providing a different indication when the-'change of condition results from. something happening at the remote station rather than from a control initiated at'the central station. However, itis obvious that a blinking arrangement or other indication can be provided "by the provision of additional contacts on the redays 300 to 396 inclusive, so that one indication is provided when a relay is'operated, and a diierent indication is provided when a change of condition takes place-While the relays are all in a releasedcondition.

Various alternative circuit constructions can be provided at the remote station as may be desired in particular application. Instead of operating a number of equipments between two positions such as trip and close, it may be desired to operate a single equipment through a larger number of different operations. In such case, a point relay can be provided for each operation and means such as the reday I 45 in Fig. 3 will be not be required to indicate the change between two positions, It will be obvious that other embodiments of this circuit can be provided to best fit particular systems, which embodiments will be obvious to those skilled in the art after a consideration of the foregoing disclosure.

Itis apparent from the above that there is provided a supervisory control system which provides control of remote equipment from a central station and which provides a continuous indication at the central station as to the condition of equipment at the remote station. The equipment requires only a single communication channel to provide this operation, although in some applications it may be preferable to provide a separate channel for signals in each direction. The indicating system indicates to the operator. rst that a desired equipment has been selected so that the operator can check the condition of the equipment to be controlled before actually operating the control. Then after the control is operated a new indication is transmitted indicating that the desired control has actually been efrfected. This control comes directly from the equipment controlledand indicates the actual operating condition and not merely that some control is provided at the remote station which is intended to produce the desired operation of the equipment.

The system also. provides indication of any change in the operating condition of the equipment whether or not this is in response to a control operated at the central station, or by any other means such as automatic operation of a circuit breaker or operation by some condition at the remote station. The operator at the central station can tell by the indication whether the change in condition resulted from a control actuated at the central station. This is particularly advantageous when an operator is not always present at the central station as it would indicate when an equipment changed to a diiierent condition and then changed back while the operator was not observing the control panel. The system can be used to control and supervise a large number of diiierent equipments and includes provisions so that in the event a number of equipments are caused to change their operating condition at the same time or at about the same time, the signals indicating the condition can be transmitted over a single channel by spacing the signals in time. The signals are then transmitted in a given sequence which is independent of the sequence in which the operations took place. i

By the use of an interlocking arrangement on the control panel, improper operation oi the control is minimized. The panel indicates when the system is busy to further assist the operator. As previously stated the indications on the panel are changed immediately upon any change in the condition of operation and this enables the operator to merely observe the control panel to determine the actual operating condition of all equipment at the remote station. As previously stated the operator can check these indications by causing the system to scan the contacts associated with each equipment so the operator can thereby check the operation of the remotely controlled equipment at will.

The supervisory control system disclosed provides a large number of desired operations and is adaptable to various systems requiring remote supervisory control. Considering the operations performed by the system, the construction thereof is very simple and requires a very small amount of equipment. The entire system is designed so that the operations are not critical and therefore the maintenance required is reduced to a minimum.

It is apparent that the arrangement for storing signals so that a plurality of operations taking place at the same time can be identied by signals transmitted in sequence may be used in other applications than that disclosed. This arrangement can be used, for example, at the central station when it is desired to send control signals from a plurality of spaced panels, and have the signals held separate from each other and transmitted in sequence.

Although one embodiment of the invention has been described which is illustrative thereof, it is obvious that various changes and modifications can be made therein without departing from the intended scope of the invention as dened in the appended claims.

We claim:

l. A system for indicating the operating condition of a plurality of items of equivalent including in combination, a plurality of relays inclividually associated with said items and operated thereby when with the operating condition of the associated item changes, a source of a plurality of signals having different characteristics, means coupled to said items and to said source for transmitting predetermined ones oi said signals to indicate the condition of each of said items, said transmitting means being rendered operative when one oi said relays operates and including selector means selectively providing connection with said relays in nxed sequence, said selector means applying signals to said transmitting means when connection is established with operated relays to transmit signals indicating the condition of the item of equipment associated therewith, and means for causing operation of all or said relays whereby signals indicating the condition of all said items are transmitted in sequence.

2. A system for controlling a plurality ci items of equipment and indicating the operating condition thereof including in combination, control means individually coupled to said items for selectively controlling the same in response to predetermined control signals, switch means individually associated with said items providing various diiierent connections depending upon the operating condition of the items, a plurality of circuits individually associated with said items and coupled to said control means and to said switch means and each including a relay responsive to operation of either said control means or said switch means of said associated item, a source of a plurality of signals having diiierent characteristics, and transmitting means including a stepping switch having a plurality of levels each with Xed contacts and a movable Contact, and having means for moving said movable contacts, said xed contacts oi one level being connected to said relays, said xed contacts of a second level being connected to said switch means, and said iixed contacts of at least one additional level being connected to said source or signals, a control circuit connected to said movable contact of said rst mentioned level of said stepping switch for moving all said movable contacts to positions corresponding to each item of equipment in response to operation of any one of said relays, and including a time-constant network for arresting motion of said movabie contacts for a selected interval whenever said movable contact of said first mentioned level engages a fixed contact connected to an operated one of said relays, an output circuit, a second control circuit connected to movable contact of said second level for controlling the application of signals from said additional level to said output circuit, said output circuit operating to transmit signals from said source corresponding to the condition of each item ci equipment when the relay associated with such item is operated.

3. A system for controlling a plurality of items of equipment and indio ng the operating condition thereof, including in combination, control means including rst relays individually coupled to said items for selecting the same and second relays coupled to items for controlling the same, a holding circuit for said iirst relays including a relay for releasing the same, switch means ini vid-daily associated with said items having diierent positions depending upon the operating condition of the associated items, a plurality of point relays individually associated with said items and coupled to said rst relays and said switch means and responsive to operation thereof, an additional point relay coupled to said relay of said holding circuit and operative when said hcl circuit is released, a source of a plurality or having diiierent characteristics, a stepping switch including a plurality of levels each having xed contacts and a movable contact and means for moving said movable contacts, said fixed contacts or a nrst level being connected to said point relays, said fixed contacts of a second level being connected to said switch means, said fixed contacts ci additional levels being connected to said source of signals, and a circuit connected to said movable contact of said rst level of said stepping switch and to said moving means therefor for causing said stepping switch to operate sequentially to positions corresponding to each of said point relays when any one of said point relays is operated, said circuit operating to transmit signals identifying the operative condition of any item when the point relay thereof is operated and said stepping switch engages the xec contacts associated therewith and identifying the release of said equipment when the aforesaid additional point relay is operated.

e. A system for indicating the operating condition of a plurality of items of equipment, including in combination, switch means associated with said items having different positions depending upon the operating condition of the iterns, a plurality of point relays individually associated with said 'tems and coupled to said switch means and respon ve to operation thereof, a source oi a plurality oi signals having different characteristics, a stepping switch including a plurality of levels each having xed contacts and a movable contact and means for moving said movable contact, said nxed contacts ci a first level being connected to said point relays, said xed contacts of a second level.Y being connected to said switch means and said xed contacts of additional levels being connected to said source of signals, a control circuit connected to the movable contact of said rst level of said stepping switch and to said moving therefor -lor cousin:r said stepping switch to operate when any one of said point relays is operated to provide connection with said point relays in predetermined sequence, and including a time-constant network for arresting the operation oi said stepping switch for a selected interval whenever said movable contact of said first level engages a fixed contact connected to an operated one of said point relays,

an output circuit, and a relay having a winding connected to the movable contact o said second level and having contacts connected to the movable contacts of said additional levels and to said circuit for selectively applying tones from fixed contacts of said additional levels to said output circuit depending upon the positions of said switch means.

5. A system for controlling a plurality of items of equipment and indicating the operating condition thereof, including in combination, control means including rst relays individually coupled to said items for electing the same and second relays coupled to said items for controlling the same, a holding circuit for lirst relays including a relay for releasing the same, switch means individually associated with said items having different positions depending upon the operating condition of the associated items, a plurality of point relays individually associated with said items and coupledL to said irst relays and said switch means and responsive to operation. thereof, an additional point relay coupled to said relay of said holdin(r circuit and operative when said holding circuit is released, a source of a plurality of signals having different characteristics, a stepping switch including a pluralit' of levels each having fixed contacts and a movable contact and means for moving asid movable contacts, said xed contacts ci a rst level being connected to said point relays, said xed contacts of a second level being connected to said switch means, said iixed contacts of additional levels being connected to said source of signals, a control circuit connected to-said iirst level of said movable Contact of said stepping switch and to said moving means therefor for causing said stepping switch to operate when any one of said point relays is operated, an output circuit operating to transmit signals identifying the operative condition of an item 'when t e point relay thereof is operated and said stepping switch engages the xed contacts associated therewith and identifying the release of said equipment when the aforesaid additional point relay is operated, and a second control circuit connected to said point relaysrior operating all said point relays to cause said output circuit to transmit signals indicating the condition of all said items in sequence.

6. A system for controlling a plurality or" items of equipment and indicating the operating condition thereof, including in combination, control means including rst relays individually coupled to said items for selecting the same and second relays coupled to said items for controlling the same, a holding circuit for said first relays including a relay for releasing the switch means associated with said items having various dierent positions depending upon the operating condition of the associated item, a plurality of point relays individually associated with said items and coupled to said iirst relays and said switch means and responsive to operation thereof, an additional point relay coupled to said relay of said holding circuit and. operative when said holding circuit is released, a source of a plurality of signals having diierent characteristics, and selector means rendered operative when any one of said point relays is operated to provide operative connection with s point relays in a predetermined sequence, said selector means being coupled to said switches and to said signal source and operating to transmit identifying signals when said selector means 25 is operatively connected to a point relay which is operated.

7.` A system for controlling a plurality of items of equipment and indicating the operating condition thereof including in combination, control means individually coupled to said items for selectively controlling the same in response to predetermined control signals, switch means individually associated with said items providingvarious different connections depending upoln the operating condition of the items, a plurality of circuits individually associated with said items and coupled to said control means and to said switch means and including relays responsive to operation of either said control means or said switch means, a source of a plurality of signals having different characteristics, and transmitting means rendered operative when any one of said relays is operated and including a selector switch providing operative connection with said circuits in a predetermined sequence, said selector switch having contacts coupled to said switch means and to said signal source and operating to transmit signals corresponding to the operative condition of `each item oi equipment when said selector means is operatively connected to the circuit associated therewith and said relay thereof is operated, and means causing operation of all of said relays whereby signals indicating the condition of all oisaid items are transmitted in sequence.

8. A system for controlling equipment at a remote station from a central station, and for indicating at said central station the condition of said equipment at said remote station, including in combination, selective means at said central station for transmitting to said remote station first signals including frequency components individually associated with said items of equipment for individually selecting said items, control means at said central station for transmitting second signals including frequency cornponents individually associated with various conditions of said items of equipment for operating the selected item, control means at said remote station individually connected to said items oi equipment, and transmitting means at said remote station controlled by said control means for transmitting to said central station signals including frequency components indicating the condition of said items of equipment, said transmitting means including means rendered responsive each time an item is selected and each time an item changes its operating condition to transmit a signal indicating the condition of such item.

9. A supervisory control system comprising a central station and a remote station, said central station including in combination; means for generating a plurality of selecting signals each having diierent characteristics; an output circuit ior transmitting said selecting signals to said remote station; and a plurality of manually operated control circuits, each of said control circuits upon actuation applying a diierent one of said selecting signals 'to said output circuit; said remote station including in combination; a plurality of items of equipment to be individually selected by said selecting signals; signal separator means for applying each of said selecting signals to a different one of said items generating means for producing a plurality of indicating signals each having different characteristics; an output circuit for transmitting said indicating signals to said central station; a selector mechanism for sequentially applying said indicating signals to said last mentioned output circuit; a plurality of point relays respectively associated with said items, each of said point relays being operated in response to the selection of its associated item by one of said selecting signals from said central station and also being operated in response to a change in the operating condition of its associated item, the operation of any of said point relays actuating said selector mechanism and causing it sequentially to supply to said last mentioned output circuit indicating signals corresponding to each operated one of said point relays.

lO. A supervisory control system comprising a central station and a remote station, said central station including in combination: means for generating a plurality of selecting signals and at least one control signal each having different characteristics; an output circuit for transmitting said selecing signals and said control signal to said remote station; a plurality of manually operated control circuits, each of said control circuits upon actuation applying a diierent one of said selecting signals to said output circuit; and a further manually operated control circuit for applying said control signal to said output circuit; said remote station including in combination: a plurality of items of equipment to be individually selected by said selecting signals; control means responsive to an applied signal for operating any of said items selected by said sen lecting signal; signal separator means for applying each of said selecting signals to a different one of said items, and for applying said control signal to said control means; generating means for producing a plurality of indicating signals each having different characteristics; an output circuit for transmitting said indicating signals to said central station; a selector mechanism for sequentially applying said indicating signals to said last mentioned output circuit; a plurality of pointl relays respectively associated with said tems, each of said point relays being operated in response to the selection of its associated item by one of said selecting signals from said central station and also being operated in response to a change in the operating condition of its associated item, the operation of any of said point relays actuating said selector mechanism and causing it sequentially to supply to said last mentioned output circuit indicating signals corresponding to each operated one oi said point relays.

11. A supervisory control system comprising a central station and a remote station, said central station including in combination; means for generating a plurality of selecting signals and a release signal each having different characteristics; an output circuit for transmitting said selecting signals and said release signal to said remote station; a plurality of manually operated control circuits, each of said control circuits upon actuation applying a diierent one oi said selecting signals to said output circuit; and a further manually operated control circuit for applying said release signals to said output circuit; said remote station including in combination; a plurality ci items of equipment to be individually selected by said selecting signals; release means responsive to an applied signal for releasing any one of said items selected by sai-d selecting signals; signal separator means for applying each of said selecting signals to a different one of said items, and for applying said release signal to said release means; generating means for producing a plurality of indicating signals each having different characteristics; an output circuit for transmitting said indicating signals to said central station; a selector mechanism for sequentially applying said indicating signals to said last mentioned output circuit; a plurality of point relays respectively associated with said items, eacli of said point relays being operated in response to the selection of its associated item oy one of said selecting signals from said central station and also being operated in response to a change in the operating Condition of its associated item; and a further point relay operated in response to actuation ci said release means by said release signal, the operation of said point relays actuating said selector mechanism and causi it sequentially to supply to said last last mentioned output circuit indicating signals corresponding to caen operated one of said point relays.

l2. A supervisory control system comprising a central station and a remote station, said central station including in combination; means for generating a plurality ci" selecting signals each llaving diileient characteristics; an output circuit for transmitting said selecting signals to said remote station; and a plurality of manually operated control circuits, each of said control circuits upon actuation applying a dierent one of said selecting signals to output circuit; said remote station inclu-ding in combination: a plurality of items of equipment to ce individually7 se iected by said selecting signals; signal separator means for applying each oi said selecting signals to a dirle-rent one or said items; generating means for producing a plurality or indicating signals each having direrent characteristics; an output circuit for transmitting said indicating signals t0 said central station; a selector mechanism for sequentially applying a first series of said indicating signals to said last mentioned output circuit and for sequentially deriving a second series of said indicating signals concurrently with said iirst series; a plurality of point relays respece tively associated with said items, each or said point relays being operated in response to the selection of its associated item by one or said selecting signals from said central station and also being operated in response to a change in the operating condition of its associated item, the operation of any one of said point relays actuating said selector mechanism and causing it sequentially to supply to said last mentioned output circuit indicating signals -trom said rst series corresponding to eacn operated one of said point relays; and circuit means responsive to the operating condition of each of said items of equipment for causing said selector to supply indicating signals from said second series to said output circuit representing the operating condition or" the items or equipment respectively associated with each operated one oi" said point relays.

13. A supervisory control system comprising a central station and a remote station, said central station including in combination; means for generating a scanning signal; an output circuit for transmitting said scanning signal to said remote station; and a manually operated control circuit for applying said scanning signal to said output circuit; said remote station including in coinbination: a plurality of items of equipment to be controlled from said central station; generating means for producing a plurality of indicating signals each having diierent characteristics; an output circuit ror transmitting said indicating signals to said central station; a selector mechanism for sequentially applying a irst series of said indicating signals respectively representing said items of equipment to said last mentioned output circuit and for sequentially deriving a second series of said indicating signals concurrently with said rst series; a plurality of point relays respectively associated with said items, eacli said point relays 1oeing operated in response to said scanning signal, the operation ci said point relays actuating said selector mechanism and causing it sequentially to supply said first series of indicating signals to said last mentioned output circuit; and circuit means responsive to the operating condition of each or said items of equipment for causing said selector to Supply indicating signals from said second series to said cute put circuit concurrently with the signals of said first series and respectively indicating the operating condition of each of said items.

14. A system for indicating the operating condition of a plurality of items of continent including in combination, a plurality of point re lays individually associated with said items and operated when the operating condition of the associated item changes, generating means for producing a plurality of indicating signals eac!" having different characteristics, an output circuit, a selector mechanism for sequentially deriving indicating signals from said generating means respectively representing the operating condition of each oi said items, a iirst control circuit for actuating said selector whenever one oi' said point relays is operated, and a second control circuit for causing said selector to supply seguentially to said output circuit only such indicating' signals corresponding to the aforesaid items w ose associated point relays are operated.

l5. A system for indicating the operating condition of a plurality of iten s or' equipment including in combination, a plurality of point relays individually associated with said items and operated when the operating conditions or the associated item changes, generating means for producing a plurality of indicating signals having diiierent characteristics, an output circuit, a selector mechanism for sequentially deriving indicating signals from said generating means respectively representing the operating condition of each of said items, a control circuit for actuating said selector whenever one of said point relays is operated, and a time-constant network included in said control circuit for causing said selector to supply sequentially to said output circuit only such indicating signals corresponding to the aforesaid items whose associated point relays are operated.

16. A central station for controlling equipment at a remote station including in combination: generating means for developing a release signal of distinctive characteristics; an output circuit including a first time-constant network, and including a rst relay means for impressing the release signal on an output terminal for transmission to the remote station; a control circuit including a second time-constant network, and. including second relay means for impressing release signal on said output circuit; and a manually operated control for energizing said first relay means to completea connection from control circuit to said output terminal, for ccmpleting an energizing circuit for said second relay means thereby to complete a connection from said generating means to said output terminal, to break an energizing circuit to said rlrst time-constant network, and to maire an energizing circuit to said second time-constant network; said rst relay means remaining energized for a selected time interval determined by said lirst time-constant network and said second relay means re- A maining enerized for a selected time interval after said first mentioned time interval determined by said second time-constant network.

17. A central station for controlling equipment at a remote station including in combination: generating means for developing a release signal of distinctive characteristicsand for developing a plurality of control signals, also of individual distinctive characteristics; an output circuit including a first time-constant network, and including a rst relay means for impressing the release signal and control signals on an output terminal for transmission to the remote station; a control circuit including a second time-constant network, and including second relay means for impressing said release signal on said output circuit; and a manually operated release control for energizing said rst relay means so as to complete a connection from said control circuit to said output terminal, so as to complete an energizing circuit for said second relay means thereby to supply said release signal to said output terminal and interrupt the application of said control signals to said output terminal, so as to break an energizing circuit to said rst time-constant network, and so as to make an energizing circuit to said secondn time-constant network; said first relay means remaining energized for a selected time interval determined by said iirst time-constant network and said second relay means remaining energized for a selected time interval after said first mentioned time interval determined by said second time-constant network.

18. A central station for controlling equipment at a remote station including in combination: generating means for developing a release signal of distinctive characteristics and for developing at least one control signal also of distinctive characteristics; an output circuit including a first time-constant network, and including a first relay means for impressing signals applied to said output circuit on an output terminal for transmission to the remote station; a control circuit including a second time-constant network, and including second relay means for impressing said release signal on said output circuit and for interrupting the application of said control signal on said output circuit; and a manually operated control for establishing a connection from said generating means to said control circuit to supply said control signal to said control circuit and for energizing said first relay means so as to complete a connection from said control circuit to said output terminal; said rst relay means remaining energized for a selected time interval determined by said rst time-constant network, and then causing said second relay means to be energized for a further selected time interval determined by said second time-constant network to interrupt the application of said control signal to said output circuit and apply said release signal to said output circuit.

19. A remote station having at least one item of equipment to be controlled by a central station, said remote station including in combination: an actuating device for the aforesaid item including a trip coil and a close coil; a control relay for said actuating device responsive to a first signal from the aforesaid central station for establishing an energizing connection to one end of each of said coils of said actuating device; a trip relay responsive to a second signal from said central station for completing an energizing connection to the other end of said trip coil; a close relay responsive to the third signal from said central station for completing an venergizing connection to the other end of said close coil; generating means for developing a plurality of indicating signals; a selector mechanism for selecting a iirst indicating signal having distinctive characteristics representing the aforesaid item, and for selecting second and third indicating signals having distinctive characteristics respectively representing an open and closed condition of said item; a point relayresponsive to said first signal from said central station and to a change in condition of said item for actuating said selector to select the aforesaid indicating signals; an output circuit for transmitting said indicating signals to the central station; circuit means for applying said rst indicating signal to said output circuit upon activation of said selector by said point relay; and a'relay included in said last-mentioned circuit means responsive to the condition of said item for supplying a selected one of said second and third indicating signals to said output circuit.

l 20. A remote station having at least one item of equipment to be controlled by'a central station, said remote station including in combination: generating means for developing a plurality of indicating signals; a selector mechanism for selecting a rst indicating signal having distinctive characteristics representing the aforesaid item, and for selecting second and third indicating signals having distinctive characteristics respectively representing an open and closed condition of said item; a point relay responsive to a change in condition of said item for actuating said selector to select the aforesaid indicating signals; an output circuit for transmitting said indicating signals to the central station; cir.. cuit means for applying said first indicating signal to said output circuit upon actuation oi' said selector by said point relay; and a relay included in said last mentioned circuit means responsive to the condition of said item for supplying a selected one of said second and third indicating signals to said output circuit.

JOHN A. DOREMUS. HERBERT C. WATERMAN.

References Cited in the ille of this patent UNITED STATES PATENTS Number Name Date 1,674,127 Bellamy June 19, 1928 1,714,973 White May 28, 1929 1,763,879 Burns June 17, 1930 1,786,805 Wensley Dec. 30, 1930 1,790,188 White Jan. 27, 1931 1,790,866 Hudd Feb. 3, 1931 2,059,896 Oliver Nov. 3, 1936 2,280,144 Derr Apr. 21, 1942 2,298,907 Stewart Oct. 13, 1942 2,408,037 Bowsher Sept. 24, 1946 2,444,243 Breese June 29, 1948 2,543,869 Rees Mar. 6, 1951 2,616,959 Breese Nov. 4, 1952 

